Core facilities will have specialized nitrogen and oxygen gas generation facilities to minimize costs that would otherwise be incurred in gas tank purchases for the high volume gas use required for intermittent and chronic hypoxia studies. The Core unit will also include computer controlled control equipment to regulate gas mixtures according to sensors in the chambers to allow the exposure of rats to conditions of chronic and intermittent hypoxia. These rats will be used in studies by Drs. Gozal, Siegel, McGinty and Szymusiak. Core facilities will also include histology facilities to be used for immunohistochemistry and other standard histology stains by Drs. Chase, Gozal, Siegel, McGinty and Szymusiak. Finally, the Core will contain an administrative unit to be used by all investigators to coordinate SCOR meetings and data and manuscript exchange, visits by invited faculty, and required reports.